Ring electrode with porous member

ABSTRACT

A lead assembly having a ring electrode is adapted for implant and for connection to a system for monitoring or stimulating cardiac activity. The lead assembly includes a first porous member disposed around the ring electrode at the distal end of the lead assembly, which can be used as a sensing or pacing interface with the cardiac tissue. In addition, a second porous member is disposed over the first porous member and is electrically coupled with the ring electrode.

TECHNICAL FIELD

[0001] The present invention relates generally to leads for conductingelectrical signals to and from the heart. More particularly, it pertainsto a ring electrode for pacing electrical signals from the heart.

BACKGROUND

[0002] Leads implanted in or about the heart have been used to reversecertain life threatening arrhythmias, or to stimulate contraction of theheart. Electrical energy is applied to the heart via the leads to returnthe heart to normal rhythm. Leads have also been used to sense in theatrium or ventricle of the heart and to deliver pacing pulses to theatrium or ventricle. Technically, the pacemaker or the automaticimplantable cardioverter defibrillator (AICD) receives signals from thelead and interprets them. In response to these signals the pacemaker canpace or not pace. The AICD can pace, not pace or shock, and not shock.In response to a sensed bradycardia or tachycardia condition, a pulsegenerator produces pacing or defibrillation pulses to correct thecondition. The same lead used to sense the condition is sometimes alsoused in the process of delivering a corrective pulse or signal from thepulse generator of the pacemaker.

[0003] Cardiac pacing may be performed by the transvenous method or byleads implanted directly onto the ventricular epicardium. Most commonly,permanent transvenous pacing is performed using a lead positioned withinone or more chambers of the heart. The lead may also be positioned inboth chambers, depending on the lead, as when a lead passes through theatrium to the ventricle. sense electrodes may be positioned within theatrium or the ventricle of the heart. For pacing applications, the leadmay be positioned in cardiac veins or arteries.

[0004] Positioning an electrode disposed on a distal end of a leadwithin a vein or artery presents additional challenges in maintainingthe lead in a fixed position since the distal end of the lead does notabut a surface. These challenges also may result in poor pacing andsensing capabilities of the electrode.

[0005] Therefore, there is a need for a lead having an electrode forpositioning within cardiac veins, or arteries that allows for fixationtherein. In addition, what is needed is a lead which provides desirablepacing and sensing properties.

SUMMARY

[0006] A body-implantable lead assembly includes a lead, one end beingadapted to be connected to electrical supply for providing or receivingelectrical pulses. The lead extends to a distal end which is adapted tobe connected to tissue of a living body. The lead also has a sheath ofmaterial inert to body materials and fluids and at least one conductorextending through the lead body.

[0007] The distal end of the lead assembly is adapted for implantationproximate to or within the heart while connected with a system formonitoring or stimulating cardiac activity. In addition, the distal endof the lead assembly is implanted in cardiac veins or arteries,depending on the application. The distal end includes a ring electrodeelectrically coupled with a first porous member electrically coupledwith the ring electrode. A conductor coil is disposed within the leadbody and is electrically coupled with the ring electrode.

[0008] In one embodiment, the ring electrode includes a cut out, and thefirst porous member is disposed in the cut out. The first porous memberis electrically active, and paces and/or senses the tissue once it isimplanted. In addition, the surface area of the first porous member ischanged to control electrically properties of the lead assembly. Thefirst porous member is formed of a material which is inert to a livingbody.

[0009] The first porous member, in another embodiment, includes a meshscreen. The mesh screen is formed of various materials, including, butnot limited to, platinum iridium, iridium oxide, titanium nitride,titanium oxide, diamond, tantalum. In another embodiment, the firstporous member is sputter coated on the ring electrode with liquid metal.In yet another embodiment, the first porous member is formed by etchingthe ring electrode with acid. The first porous member, in oneembodiment, is formed by laser scribing the ring electrode. In anotherembodiment, the first porous member is formed by particle blasting thering electrode. In yet another embodiment, the first porous member isformed by chemical vapor deposition of the ring electrode. The firstporous member, in another embodiment, is formed by coating the ringelectrode with diamond.

[0010] In another embodiment, a ring electrode is electrically coupledwith the conductor and a first porous member electrically coupled withthe ring electrode. A second porous member is disposed over the firstporous member, and each is electrically coupled with the ring electrode.The second porous member is bonded with the ring electrode, forinstance, by sintering or welding. The first porous member and thesecond porous member are electrically active, and can pace and/or sensethe tissue once it is implanted.

[0011] The above-described lead assembly provides several benefitsincluding increased sensing and pacing properties. Furthermore, thefirst and/or second porous members will assist in retaining theelectrode assembly in a desired location due to the tissue ingrowth.

[0012] These and other embodiments, aspects, advantages, and features ofthe present invention will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the art byreference to the following description of the invention and referenceddrawings or by practice of the invention. The aspects, advantages, andfeatures of the invention are realized and attained by means of theinstrumentalities, procedures, and combinations particularly pointed outin the appended claims and their equivalents. Brief Description of theDrawings is an elevational view illustrating a lead assembly constructedin accordance with one embodiment of the assembly. is cross-section viewof a distal end of a lead assembly constructed in accordance with oneembodiment of the assembly. is cross-section view of a distal end of alead assembly constructed in accordance with one embodiment of theassembly. is cross-section view of a distal end of a lead assemblyconstructed in accordance with one embodiment of the assembly. iscross-section view of a distal end of a lead assembly constructed inaccordance with one embodiment of the assembly. is cross-section view ofa distal end of a lead assembly constructed in accordance with anotherembodiment of the assembly.

DETAILED DESCRIPTION

[0013] In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those skilled in the art to practice the invention, and it is tobe understood that other embodiments may be utilized and that structuralchanges may be made without departing from the scope of the presentinvention. Therefore, the following detailed description is not to betaken in a limiting sense, and the scope of the present invention isdefined by the appended claims and their equivalents.

[0014]FIG. 1 illustrates a lead 100 for delivering electrical pulses tostimulate a heart and/or for receiving electrical pulses to monitor theheart. The lead 100 has a distal end 102 adapted for implant within abody, for instance within a vein, and a proximal end 104. The proximalend 104 has a connector terminal which electrically connects the variouselectrodes and conductors within the lead 100 to a pulse generator 120and signal sensor. The terminal connector provides for the electricalconnection between the lead 100 and the pulse generator 120. The pulsegenerator 120 contains electronics to sense various electrical signalsof the heart and also to produce current pulses for delivery to theheart.

[0015] The lead 100 includes a lead body 115, an elongate conductor 116contained within the lead body 115, and at least one electrode assembly130. The lead body 115 is covered by a biocompatible insulatingmaterial. Silicone rubber or other insulating material is used forcovering the lead body 115. In one embodiment, the electrode assembly130 is disposed proximate to the distal end 102 of the lead 100. Inanother embodiment, the electrode assembly 130 is disposed between thedistal end 102 and the proximal end 104 of the lead 100.

[0016] The conductor 116 comprises a coil, which has been shown to becapable of withstanding constant, rapidly repeated flexing for years.The coiled construction is wound relatively tightly providing a maximumnumber of conductor turns per unit length, which allows for straindistribution. The spirally coiled spring construction of the conductoralso permits a substantial degree of elongation, within the elasticlimits of the material, as well as distribution along the conductor offlexing stresses which otherwise might be concentrated at a particularpoint.

[0017] The elongate conductor 116 defines a lumen 117 therein, as shownin FIGS. 2 and 3, and thereby is adapted to receive a stiffening styletthat extends through the length of the lead 100. Referring again to FIG.1, the stylet stiffens the lead 100, and can be manipulated to introducean appropriate curvature to the lead 100. The manipulation of the styletfacilitates the insertion of the lead 100 into and through a vein andthrough an intracardiac valve to advance the distal end 102 of the lead100 into, for example, the right ventricle of the heart. A stylet knobis coupled with the stylet for rotating the stylet, advancing theconductor into tissue of the heart, and for manipulating the lead 100.

[0018] The electrode assembly 130 is adapted to be coupled with tissueof a patient, for example, within a heart, or within a vein or artery150 (FIG. 3). Referring to FIG. 2A, the electrode assembly 130, includesa ring electrode 132. The ring electrode 132 includes a first porousmember 134. In one embodiment, the first porous member 134 is fullydisposed over the ring electrode 132. Alternatively, the first porousmember 134 is partially disposed over the ring electrode 132, or thefirst porous member 134 is disposed completely around the circumferenceof the ring electrode 132. In one embodiment, the first porous member134 comprises a mesh 135 made of platinum wire, where the mesh 135 isdisposed over the ring electrode 132.

[0019] The first porous member 134 is formed by creating a texture orincreasing the surface area directly on the ring electrode 132. Forinstance, a conductive material 137 is coated on the ring electrode 132,as shown in FIG. 2B. In another embodiment, as shown in FIG. 2D, a layerof material from the ring electrode 132 is removed, exposing a texturedsurface 141 to form the first porous member 134. Other processes forforming the first porous member 134 include liquid metal coating,electrode burning, laser scribing, acid etching, mechanical abrasion,particle blasting, thermal spray coating, chemical vapor deposition,plasma etching, diamond coating, and powder metallurgy such as castingor forming processes. Using these processes allows for the surface areaof the ring electrode 132 to increase, thereby increasing the sensingand pacing abilities of the ring electrode 132.

[0020] The first porous member 134 is of a porous construction, made ofelectrically conductive, corrosion resistant material. One example of asuitable material for the first porous member 134 is platinum iridium.Other suitable materials include diamond, iridium oxide, titaniumnitride, titanium oxide, platinum, titanium, and tantalum. Using a firstporous member 134 having a porous construction allows for fibroticingrowth, which provides for a further anchoring the electrode and alsoincreases the sensing capability of the lead 100 by increasing thesurface area in contact with the cardiac tissue. The surface area of thefirst porous member 134 can be changed to control electricallyproperties of the lead assembly.

[0021] The first porous member 134 is disposed, in one embodiment,within a cut out 136 disposed within the ring electrode 132, as shown inFIG. 2C. The cut out 136 is not limited to any particular shape. Forinstance, the cut out 136 comprises in one embodiment one or more cutsto the outer circumference of the ring electrode 132. In anotherembodiment, the cut out 136 comprises an annular cut out. The firstporous member 134, in another embodiment, is physically and/orelectrically attached to the ring electrode 132, such as by welding orsoldering. Other methods for attaching the first porous member 134 tothe ring electrode 132 include, but are not limited to metal bonding,diffusion bonding, or an interference fit between the first porousmember 134 and the cut out 136. Other attachment methods may be usedwithout departing from the scope of that described herein.

[0022] In another embodiment, illustrated in FIG. 3, the electrodeassembly 130 includes a ring electrode 132, which is known to thoseskilled in the art. Disposed over the ring electrode 132 is a firstporous member 134, as discussed above. The first porous member 134 isdisposed partially over the ring electrode 132. Alternatively, the firstporous member 134 is disposed completely around the circumference of thering electrode 132. The electrode assembly 130 further includes a secondporous member 140, which is disposed over the first porous member 134.The second porous member 140 is wider than the first porous member 134.The second porous member 140 is physically and/or electrically attachedto the ring electrode 132 at 146, such as by welding, applyingconductive adhesive, or crimping. In another embodiment, the secondporous member 140 is bonded to the first porous member 134 and/or thering electrode 132 by sintering.

[0023] In one embodiment, the second porous member 140 comprises a meshformed of wire, such as platinum. In another embodiment, the secondporous member 140 is formed by creating a texture or increasing thesurface area directly on the ring electrode 132 and the first porousmember 134. For instance, a conductive material is coated on the ringelectrode 132 and the first porous member 134. Other processes forforming the second porous member 140 having an increased texture orsurface area include, but are not limited to, liquid metal coating,electrode burning, laser scribing, acid etching, mechanical abrasion,particle blasting, thermal spray coating, chemical vapor deposition,plasma etching, diamond coating, and powder metallurgy such as castingor forming processes. Using these processes allows for the surface areaof the ring electrode 132 to increase, thereby increasing the sensingand pacing abilities of the ring electrode 132.

[0024] The second porous member 140 is of a porous construction, made ofelectrically conductive, corrosion resistant material. One example of asuitable material for the second porous member 140 is platinum iridium.Other suitable materials include, but are not limited to diamond,iridium oxide, titanium nitride, titanium oxide, platinum, titanium, andtantalum. A second porous member 140 having a porous construction allowsfor fibrotic ingrowth, which provides for a further anchoring theelectrode within the heart or within a vein 150 and also increases thesensing capability of the lead 100 by increasing the surface area incontact with the cardiac tissue.

[0025] The above-described lead assembly provides several benefitsincluding increased sensing and pacing properties. Furthermore, thefirst and/or second porous members will assist in retaining theelectrode assembly in a desired location due to the tissue ingrowth. Thelead assembly is also beneficial in applications where the ringelectrode is disposed in a larger vein or artery where it is otherwisedifficult to position and/or maintain the ring electrode against thewall of the surrounding tissue.

[0026] It is to be understood that the above description is intended tobe illustrative, and not restrictive. Although the use of the lead hasbeen described for use in a cardiac pacing system, the lead could beapplied to other types of body stimulating systems. Many otherembodiments and applications will be apparent to those of skill in theart upon reviewing the above description.

What is claimed is:
 1. A lead assembly comprising: a lead body extendingfrom a proximal end to a distal end, the distal end of the lead bodyadapted to be disposed within a vein; an elongate conductor coildisposed within the lead body; a ring electrode electrically coupledwith the conductor coil, the ring electrode disposed proximate to thedistal end of the lead body; and a first mesh screen electrically andmechanically coupled with the ring electrode, the first mesh screendisposed over and around the ring electrode, the first mesh screenformed of electrically conductive, corrosion resistant material.
 2. Thelead assembly as recited in claim 1, the ring electrode including a cutout therein, and the first mesh screen is disposed within the cut out ofthe ring electrode.
 3. The lead assembly as recited in claim 1, furthercomprising a second mesh screen disposed over and around the first meshscreen, the second mesh screen mechanically and electrically coupledwith the ring electrode, the second mesh screen formed of electricallyconductive, corrosion resistant material.
 4. The lead assembly asrecited in claim 3, wherein the second mesh screen is wider than thefirst mesh screen.
 5. The lead assembly as recited in claim 1, whereinthe first mesh screen is formed of platinum iridium.
 6. The leadassembly as recited in claim 1, wherein the first mesh screen is formedof iridium oxide.
 7. The lead assembly as recited in claim 1, whereinthe first mesh screen is formed of titanium nitride.
 8. The leadassembly as recited in claim 1, wherein the first mesh screen is formedof titanium oxide.
 9. The lead assembly as recited in claim 1, whereinthe first mesh screen is formed of diamond.
 10. The lead assembly asrecited in claim 1, wherein the first mesh screen is formed of tantalum.11. A lead assembly comprising: a lead body extending from a proximalend to a distal end; a conductor disposed within the lead body; a ringelectrode electrically coupled with the conductor; and a first porousmember electrically coupled with the ring electrode.
 12. The leadassembly as recited in claim 11, wherein the first porous member issputter coated on the ring electrode with liquid metal.
 13. The leadassembly as recited in claim 11, wherein the first porous member isformed by etching the ring electrode with acid.
 14. The lead assembly asrecited in claim 11, wherein the first porous member is formed by laserscribing the ring electrode.
 15. The lead assembly as recited in claim11, wherein the first porous member is formed by particle blasting thering electrode.
 16. The lead assembly as recited in claim 11, whereinthe first porous member is formed by chemical vapor deposition of thering electrode.
 17. The lead assembly as recited in claim 11, whereinthe first porous member is formed by coating the ring electrode withdiamond.
 18. A lead assembly comprising: a lead body extending from aproximal end to a distal end, the lead body formed of a biocompatibleinsulating material, the distal end of the lead body adapted to bedisposed within a vein; an elongate conductor coil disposed within thelead body, the elongate conductor coil defining a lumen therein, thelumen adapted to receive a stiffening stylet therein; a ring electrodeelectrically coupled with the conductor coil, the ring electrodedisposed proximate to the distal end of the lead body, the ringelectrode including a cut out therein; a first mesh screen electricallyand mechanically coupled with the ring electrode, the first mesh screendisposed over and around the ring electrode within the cut out of thering electrode, the first mesh screen formed of electrically conductive,corrosion resistant material; and a second mesh screen disposed over andaround the first mesh screen, the second mesh screen mechanically andelectrically coupled with the ring electrode, the second mesh screenformed of electrically conductive, corrosion resistant material.
 19. Amethod for forming a lead assembly comprising: coupling a conductordisposed within a lead body with a ring electrode; increasing thesurface area of the ring electrode; disposing a second porous memberformed of a conductive material over the ring electrode and over theincreased surface area of the ring electrode; and mechanically couplingthe second porous member with the lead body and electrically couplingthe second porous member with the ring electrode.